It would also be interesting to know whether this is really just about "John's" karma-based society. I assume that the mother just used this to illustrate her own desperation with her son.

I don't think any "sane" person who explores funny ideas will be kept in any facilty without any other elements justifying the space that he's taking. If John needs help because his problem is more serious since he's seriously losing touch of "reality", then it will be good for him to find assistance. He may be even grateful for it. "Assistance" could consist of medication but more importantly of therepeutic sessions adapted to his specific problem, or he may be directed to self-help groups. There's always an interest there to put the patient back in charge of her own life asap, if possible.

To me it appears a bit immature to blame the mother and declare John "not mad".

"Mad" in any case speaks of some psychological imbalance. The world is full of those, true. But we all look for balance even if imbalance is an option and society is fairly tolerant of it.